1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming system.
2. Description of Related Art
Conventionally, there have been known sheet processing apparatuses which stack and align a predetermined number of sheets of paper on which images are formed by an image forming apparatus, and perform post-processing such as folding, binding and trimming on the sheets to form booklets.
In such sheet processing apparatuses, there has been known a configuration which is provided with a stacking section to stack a predetermined number of following sheets during the folding or binding.
It has been known to provide a stacking section with a vertical alignment member which aligns the ends in the conveyance direction of stacked sheets and a pair of width alignment plates which aligns the ends in the width direction orthogonal to the conveyance direction of the sheets that are aligned by the vertical alignment member provided in the stacking section. The pair of width alignment plates presses the both ends in the width direction of the sheets to align the width direction of the sheets at the same time or after the vertical alignment (for example, see Japanese Patent Application Laid Open Publication No. 2008-115010).
Generally, in the width alignment operation of sheets as described above, both ends in the width direction of sheets are pressed by the pair of horizontal alignment plates approaching each other so as to have a slightly smaller interval than the sheet width, and thus the width alignment can be performed firmly even when there are gaps in width among the individual sheets.
However, sheet processing apparatuses which perform such width alignment operation have a problem that the sheets bounce due to the rebound when the pair of horizontal alignment plates is moved away from the sheets after the width alignment operation and a gap occurs between the central position in the width direction of the conveyance path and the central position in the width direction of the sheets.